1. Field of the Invention
This invention is related to a generator for absorption refrigerators in which, for instance, water is used as a refrigerant and a salt solution such as lithium bromide is used as an absorbing solution.
2. Description of the Prior Art
As a generator of this type, for instance, that disclosed in the Japanese Patent Application Laid-Open No. 243670/1988 official gazette is known.
The generator proposed herein is constructed such that a group of heat transfer pipes which can transmit high temperature steam are placed in the lower portion within the shell main body. A space (steam chamber) for generating refrigerant vapor is provided above the absorbing solution which is injected so as to enable the heat transfer pipes to be dipped, and an eliminator is further provided in the shell upper portion to isolate the absorbing solution accompanying the refrigerant vapor.
A generator of the above construction is a so-called open type heat exchanger which has a space for the refrigerant to freely vaporize, and the heating and concentrating of the absorbing solution is by means of pool boiling.
There are two stages in a heat transfer process in which an absorbing solution is heated by heat transfer pipes in a generator. The first one is convective heat transfer which occurs when the degree of subcooling is decreased because of a subcool state in which the absorbing solution supplied to the generator is lower than the saturation temperature, and it is further increased to a temperature required for causing a phase change. The second stage is heat transfer involving a phase change, which occurs when the absorbing solution overheated by the convective heat transfer of the first stage is boiled or the surface vaporization at the level takes place.
In the above-mentioned conventional generator, since the absorbing solution has a free level throughout the generator, the absorbing solution, after having entered the generator, flows at an extremely low speed, and thus the convective heat transfer portion inherently has low heat transfer characteristics corresponding to free convective heat transfer. That is, even if the absorbing solution is injected into the generator using a pump or the like, the pressure at the time of injection is opened to the free level and does not directly act as a pressure fluidizing the absorbing solution, so that the fluidizing speed of the absorbing solution becomes very low and heat exchange cannot fully be performed at the surface of the heat transfer pipes.